1. Field of the Invention
The present invention relates to a printing device, more specifically, to an ink jet printing device in which heat is applied to a recording sheet during a printing operation.
2. Description of the Related Art
There has been known an ink jet printing device capable of printing a high quality image on a recording sheet. Especially an ink jet printing device using hot melt ink has been well known for capability of printing an image at high speeds. The hot melt ink is in a solid state at room temperature and melted when heated. A conventional hot melt ink jet printing device includes a print head, a platen, and a heater. The heater is attached on a lower surface of the platen. The print head has a nozzle surface formed with a plurality of nozzles. The print head is away from the platen such that the nozzle surface confronts an upper surface called a printing surface of the platen. During printing operation, the hot melt ink is melted and supplied to the print head. Also, the platen is heated by the heater. When a recording sheet is placed on the printing surface of the platen, melted ink is ejected through the nozzles of the print head toward the recording sheet, thereby forming an image on the recording sheet. Because the recording sheet is heated by the heat from the heater, ink ejected onto the recording sheet can be reliably fixed onto the recording sheet. Thus formed image is excellent in resistant to fading.
However, when the recording sheet is heated on the platen, moisture contained in the recording sheet evaporates. This may cause edges of the recording sheet to curl up toward the print head. When the recording sheet contacts the nozzle surface of the print head, the recording sheet is stained. Also, this may cause recording sheet jams.
In order to overcome this problem, a distance between the printing surface and the print head may be increased. However, this degrades quality of printed images. Also, heating temperature of the printing surface may be lowered. In this case, however, ink forming the images can fix onto the recording sheet less securely.